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Re: Xen bootloader (was: Re: [Xen-devel] Xen Roadmap proposal)

To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>
Subject: Re: Xen bootloader (was: Re: [Xen-devel] Xen Roadmap proposal)
From: yhlu <yhlu.kernel@xxxxxxxxx>
Date: Thu, 13 Jul 2006 22:12:47 -0700
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, Anthony Liguori <aliguori@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Michael Loehr <MLOEHR@xxxxxxxxxx>
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kboot is some kind of initrd that it will be loaded by first kernel.

the core is first kernel that has kexec built in. and another kexec
util in user space can load the final kernel.

I'm using LinuxBIOS->first kernel-->initrd-->kexec the xen.gz.

the current kexec already support multiboot image that xen is using.

So do you mean the kexec
1. from dom0, that is used to restart xen and dom0
2. or kexec in domU that will load this own first kernel then the
final kernel in the domU.?


On 7/13/06, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
Just floating this for general comment -

For the bootloader work, we should consider Kboot:

Kboot is designed to use a "conventional" bootloader to start a Linux kernel
running "full" bootloader functionality.  This is responsible for loading and
kexec-ing the kernel the user actually wants to run.  The advantage of this
is that all the high level functionality of grub (interactive menus,
filesystem support, networking) are now provided by a full Linux environment
rather than a large special purpose codebase.

Some folks at IBM (Michael included) have been working on an update to this
called kboot_sl (system loader): http://merbach.net/kboot_sl/

The zSeries guys want this because their z/IPL bootloader doesn't have any
interactivity - rather like the domain builder.  They want to start a
default "kboot" kernel and have that display the user interface, offer
network boot options, etc, and then kexec to the "real" kernel.  Their
requirements are similar to ours, so kboot_sl is worth a look.

I think this is an approach we should look at.

It gets us:
* Interactive bootloader
* Guest kernel stored in its own filesystem
* Network boot
* Multiple filesystem support (in principle, anything that Linux supports)
* Exotic boot support (boot from http, ftp, ssh - good for developers)
* A common platform with other software

A port of Grub(2?) might also be nice to have, but I suspect that (given a
working kexec) kboot_sl will be easier to get working and will be more


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